Of the many kinds of fatigue of materials, this paper deals only with “The fatigue of ductile metals by the imposition of cyclic stresses.” It is the purpose of the paper to show that: —

1. (i) Metals have certain very human attributes.

2. (ii) They have both memory and temperament.

3. (iii) They remember with increasing resentment the stresses which have been imposed upon them.

4. (iv) They are extremely sensitive as to the appropriate moment at which to break.

The question arises of why a piece of any ductile metal, other than a ferrous one, free from any abrupt change of section, when subjected to cyclic stresses of any magnitude, however small, ultimately breaks although the maximum stress imposed is one which, if static, it could have borne indefinitely. The answer is—mainly because of its metallographic structure.

This paper does not claim to reveal any epic discoveries. In fact the technical features discussed, if perhaps not well tried are certainly well known to designers and technicians in aeronautical development. Its purpose is rather to emphasise the need for concentration in development in certain directions in the light of up-to-date combat experience with the aid of rather limited, but surprising, information on design trends of modern enemy interceptor fighters.

It is hoped that this will assist the operators, who will readily appreciate the tactical aspects, to assimilate some of the technical implications and to be able to discuss them more freely with designers and technicians.

It is well known that jet aeroplanes operate most economically, from a fuel consumption point of view, at their service ceiling and that with fighters the struggle for altitude supremacy has always been paramount from the beginning.

The first part of this paper discusses some fundamentals of Air Transport and shows how these affect the organisation of airline operators. Against this background, Part II examines some of the particular problems of the short haul operator—the side of the Industry with which the author has been associated in British European Airways.

Commercial Air Transport has existed for more than thirty years. It has made important progress, but has still a long way to go to fulfil its destiny. Although progress in developing the vehicle since the first aeroplane flew in 1903 has been highly spectacular, Air Transport itself has made a slow start. This is shown by Fig. 1 which compares the increases in passenger traffic that occurred in the first thirty years of British rail and air transport.

The relations between the various reference chords used in reports on the loading of wings (standard mean chord, mean aerodynamic chord, centroid of area chord, and so on) are reviewed. Formulae are given for the position on these reference chords of the mean aerodynamic centre of certain simple “ additional” load distributions. References to convenient methods of calculating the load distribution on an arbitrary wing are also given.